Many engines combust fuel in a combustion chamber to drive a piston. In many cases, an engine combusts fuel in a combustion chamber as part of a power cycle that includes directing air from an intake system into the combustion chamber, combusting the fuel with the air in the combustion chamber to produce combustion gas that drives a piston, and discharging the combustion gas from the combustion chamber into an exhaust system. In some cases, the engine includes an external exhaust gas recirculation system for directing combustion gas from the exhaust system to the intake system to be returned to the combustion chamber. Unfortunately, in some circumstances, such an external exhaust gas recirculation system may fail to deliver combustion gas to the intake system. For example, in some circumstances, a supercharger may drive the pressure in the intake system higher than the pressure in the exhaust system, which may inhibit delivering combustion gas to the air intake system through the external exhaust gas recirculation system.
Published U.S. Patent Application No. 2005/0076890 A1 to Seitz et al. (“the '890 application”) shows a method of internally recirculating combustion gas. The '890 application discloses opening an exhaust valve of an engine approximately 160 degrees after top dead center of a power stroke of the engine. The '890 application also discloses executing an intake valve prestroke wherein an intake valve of the engine is opened between 180 and 210 degrees after the beginning of a power stroke of the engine. The '890 application discloses that, in some limited circumstances, there is a positive pressure difference between the combustion chamber associated with the intake valve and an intake system of the engine during the intake valve prestroke. This positive pressure difference drives combustion gas from the combustion chamber into the intake system of the engine during the intake valve prestroke disclosed by the '890 application.
Although the method of the '890 application includes directing combustion gas from the combustion chamber into the intake system by opening the intake valve during the exhaust stroke, certain disadvantages persist. For example, in at least some applications and/or circumstances, executing the method disclosed by the '890 application may entail compromising between heating air in the intake system to undesirably high temperatures and delivering an undesirably small amount of combustion gas to the intake system. Opening the intake valve in a manner to deliver a large quantity of combustion gas into the intake system may provide certain advantages. However, introducing a large quantity of combustion gas into the intake system may heat air in the intake system to undesirably high temperatures. Conversely, limiting the amount of combustion gas that enters intake system to prevent undesirably heating air in the intake system may have certain drawbacks, such as causing the engine to produce undesirably large quantities of NOx in some circumstances.
The engine and methods of the present disclosure solve one or more of the problems set forth above.